Lithium diisopropylamide → 2-[(E)-2-(2-chloro-5-methoxyphenyl)ethenyl]-5-methoxy-1H-indole

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The 5-methoxy-1H-indole-2-carbaldehyde (1) was reacted with (2-chloro-5-methoxybenzyl)(triphenyl)phosphonium bromide (578) prepared as described in example 166 using the procedure described in example 37, except that the LDA and aldehyde were (sequentially) added at 0° C., the ratio of LDA:aldehyde was 1.5:1 and the reaction time was 5 h, to give (after crystallisation from CH2Cl2/hexane) the diene (579) as a pale yellow solid (the pure E isomer) (85%), mp 119–121° C. 1H NMR (CDCl3) δ 8.22 (br s, 1H), 7.29 (d, J=8.9 Hz, 1H), 7.26 (br d, J=8.7 Hz, 1H), 7.22 (d, J=16.5 Hz, 1H), 7.18 (d, J=3.0 Hz, 1H), 7.06 (d, J=16.7 Hz, 1H), 7.04 (br s, 1H), 6.88 (dd, J=8.7, 2.5 Hz, 1H), 6.77 (dd, J=8.8, 3.0 Hz, 1H), 6.59 (d, J=1.8 Hz, 1H), 3.86 (s, 3H), 3.85 (s, 3H). Found: C, 68.70; H, 5.11; N, 4.37. C18H16ClNO2 requires C, 68.90; H, 5.14; N, 4.46.

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